Implantable stroke preventing device

ABSTRACT

An implantable device for positioning in the vicinity of the bifurcation of the common carotid artery (CCA) into the internal carotid artery (ICA) and the external carotid artery (ECA), comprises a deflecting element suitable to deflect the flow of embolic material flowing in the CCS toward the ICA, into the ECA, without filtering.

FIELD OF THE INVENTION

[0001] The present invention relates to implantable stroke treatingdevices, and more specifically is concerned with a device for reducingthe risk of embolic material entering into the internal carotid arteryof an individual and blood clots (collectively and interchangeablyreferred to as “embolic material”).

BACKGROUND OF THE INVENTION

[0002] A major portion of blood supply to the brain hemispheres is bytwo arteries, referred to as common carotid arteries (CCA), each ofwhich branches off, or bifurcates as the term is at times used, into aso-called internal carotid artery (ICA) and an external carotid artery(ECA). Blood to the brain stem is supplied by two vertebral arteries.

[0003] Cerebrovascular diseases are considered among the leading causesof mortality and morbidity in the modern age. Strokes denote an abruptimpairment of brain function caused by pathologic changes occurring inblood vessels. The main cause of strokes is insufficient blood flow tothe brain (referred to as “an ischemic stroke”) which are about 80% ofstroke cases.

[0004] Ischemic strokes are caused by sudden occlusion of an arterysupplying blood to the brain. Occlusion or partial occlusion (stenosis)are the result of diseases of the arterial wall. Arterialatherosclerosis is by far the most common arterial disorder, and whencomplicated by thrombosis or embolism it is the most frequent cause ofcerebral ischemia and infarction, eventually causing the cerebralstroke.

[0005] Cardioembolism causes about 15%-20% of all strokes. Stroke causedby heart disease is primarily due to embolism of thrombotic materialforming on the atrial or ventricular wall or the left heart valve. Thesethrombi then detach and embolize into the arterial circulation. Embolilarge enough can occlude large arteries in the brain territory and causestrokes.

[0006] Cardiogenetic cerebral embolism is presumed to have occurred whencardiac arrhythmia or structural abnormalities are found or known to bepresent. The most common cause of cardioembolic stroke is nonrheumatic(non-valvular) arterial fibrillation (AF), myocardial infarction,prothetic valves, rheumatic heart disease (RHD) and ischemiccardiomyopathy.

[0007] Such disorders are currently treated in different ways such as bydrug management, surgery (carotid endarterectomy) in case of occlusivedisease, or carotid angioplasty and carotid stents.

[0008] While endarterectomy, angioplasty and carotid stenting areprocedures targeting at reopening the occluded artery, they do notprevent progression of new plaque (restenosis). Furthermore, embolismsfrom the new forming plaque in the internal carotid artery (with orwithout a stent implanted therein) can occlude smaller arteries in thebrain and cause strokes. Even more so, the above treatment methods donot prevent proximal embolic sources, i.e. embolus formed at remotesites heart and ascending aorta) to pass through the reopened stenosisin the carotid and occlude smaller arteries in the brain.

[0009] It will also be appreciated that endarterectomy is not suitablefor intracarnial arteries or in the vertebrobasilar system since thesearteries are positioned within unacceptable environment (brain tissue,bone tissue) or are too small in diameter.

[0010] Introducing filtering means into blood vessels, in particularinto veins, has been known for some time. However, filtering devicesknown in the art are generally of a complex design, which renders suchdevices unsuitable for implantation with carotid arteries, andunsuitable for handling fine embolic material. However, when consideringthe possible cerebral effects of even fine embolic material occluding anartery supplying blood to the brain, the consequences may be fatal ormay cause irreversible brain damage.

[0011] However, in light of the short period of time during which braintissue can survive without blood supply, there is significant importanceto providing suitable means for preventing even small embolic materialfrom entering the internal carotid artery, so as to avoid brain damage.

[0012] A drawback of prior art filtering means is their tendency tobecome clogged On the one hand, in order to provide efficient filteringmeans, the filter should be of fine mesh. On the other hand, a fine meshhas a higher tendency toward, and risk of occlusion.

[0013] It should also be noted that the flow ratio between the ICA andthe ECA is about 4:1. This ratio also reflects the much higher risk ofembolic material flowing into the ICA.

[0014] It is thus an object of the present invention to provide animplantable deflecting device suitable to be positioned within a bloodvessel supplying blood to the brain, and further suitable to deflectembolic material that would have flown into the internal carotid artery,into the external carotid artery, thereby preventing the entry of saidembolic material into the internal carotid artery, and thus preventingextracranial embolus to occlude small intercranial arteries in thebrain.

[0015] It is another object of the invention to provide a method forpreventing conditions associated with embolic material.

[0016] Other objects of the invention will become apparent as thedescription proceeds.

SUMMARY OF THE INVENTION

[0017] The present invention provides an implantable device forpositioning in the vicinity of the bifurcation of the common carotidartery (CCA) into the internal carotid artery (ICA) and the externalcarotid artery (ECA), comprising a deflecting element suitable todeflect the flow of embolic material flowing in the CCA toward the ICA,into the ECA.

[0018] Thus, in one aspect, the invention provides an implantabledeflecting device for implanting at the vicinity of bifurcation of thecommon carotid artery (CCA) into the internal carotid artery (ICA) andthe external carotid artery (ECA); the device comprising an anchoringmember engageable with inner walls of a carotid artery, and one or moredeflecting members for deflecting flow of embolic material into the ECA,substantially without obstructing blood flow into the ICA.

[0019] The anchoring member and the deflecting member may be integralwith one another or attached or coupled to one another. In the presentspecification the anchoring member and the deflecting member may bereferred to also as anchoring portion and deflecting portion,respectively.

[0020] By a preferred embodiment, at least the anchoring member is astent adapted for insertion via the vasculature of an individual. Theimplantable deflecting device in accordance with any of the embodimentsof the present invention may be permanently implanted or may be removedafter a period of time, depending on the course of treatment and themedical procedure.

[0021] The deflecting member may be positioned at any location thatfulfills two conditions: firstly, it does not occlude the flow of bloodinto the ICA, and secondly, it causes a deflection of the flow ofembolic material into the ECA.

[0022] The one or more deflecting member may be integrally formed withthe anchoring member or may be attached or coupled thereto either duringmanufacture, or after implanting the anchoring member within the artery.

[0023] In accordance with one specific embodiment of the invention, theanchoring member comprises a tubular portion for anchorage within theCCA with said one or more deflecting member accommodated within saidtubular portion. In accordance with this embodiment the deflectingmember generates a flow vector deflecting flow of embolic material intothe ECA.

[0024] By another specific embodiment the one or more deflecting memberis adapted for generating a centrifugal flow pattern deflecting theembolic material into the ECA Preferably, in accordance with the latterembodiment, the one or more deflecting member has a hemodynamicwing-like shape.

[0025] Alternatively, the one or more deflecting member comprises anarray of wires arranged so as to form a helical path. Such wirestypically have an imaginary point of intersection which is offset withrespect to a longitudinal axis of the common carotid artery.

[0026] By another aspect of the present invention there is provided animplantable deflecting device for implanting at the vicinity ofbifurcation of the common carotid artery (CCA) into the internal carotidartery (ICA) and the external carotid artery (ECA); the devicecomprising an anchoring member engageable with inner walls of a carotidartery, and one or more deflecting members, wherein the one or moredeflecting member is so positioned and sized so that embolic materialencountering it is deflected to flow into the ECA.

[0027] In another aspect the invention is directed to an arterial stentsuitable to be positioned in the vicinity of the bifurcation of thecommon carotid artery (CCA) into the internal carotid artery (ICA) andthe external carotid artery (ECA), comprising a deflecting device.

[0028] The invention is further directed to an arterial stent suitableto be positioned in the vicinity of the bifurcation of the commoncarotid artery (CCA) into the internal carotid artery (ICA) and theexternal carotid artery (ECA), coupled to a deflecting device.

[0029] In a further aspect, the invention is directed to the preventionof the occurrence, or the recurrence, of cerebrovascular diseases,particularly of stroke, comprising preventing the flow of embolicmaterial flowing in the CCA from accessing the ICA, by deflecting theflow of said embolic material into the ECA. Prevention of thecerebrovascular disease is achieved by implanting, permanently ortemporarily, in the vicinity of the bifurcation of the common carotidartery (CCA) into the internal carotid artery (ICA) and the externalcarotid artery (ECA), a deflecting device according to the invention.

[0030] All the above and other characteristics and advantages of theinvention will be better understood through the following illustrativeand non-limitative detailed description of preferred embodimentsthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to better understand the invention and to illustrate itin practice, non-limiting examples of some preferred embodiments willnow be described, with reference to the accompanying drawings, in which:

[0032]FIG. 1 is a schematic illustration of a deflecting device locatedwithin the common carotid artery and fitted with fluid flow divertingmeans;

[0033]FIG. 2A is a schematic perspective transparent illustration of adeflecting device of FIG. 1, according to a preferred embodiment;

[0034]FIG. 2B is a schematic top view of the device of FIG. 2A;

[0035]FIG. 2C shows the mesh-like deflecting device of FIG. 2B incross-sectional view taken along the A-A axis;

[0036]FIG. 2D is a schematic unfolded view of the device of FIG. 2Aduring delivery;

[0037]FIG. 3A is a schematic, isometric illustration of a deflectingdevice in accordance with still another embodiment located within thecommon carotid artery;

[0038]FIG. 3B is a cross-sectional view into the common carotid arteryof the deflecting member;

[0039]FIG. 4A is a schematic cross-section of a preferred embodiment ofthe device of FIG. 3;

[0040]FIG. 4B shows the positioned relationship of the device of FIG. 4Aand the ECA;

[0041]FIG. 4C schematically shows the frame of which the deflectingmember of FIG. 4B is made; and

[0042]FIG. 4D is a cross-sectional view of the deflecting element ofFIG. 4B along the axis of the artery.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0043] Attention is first directed to FIG. 1, in which there isschematically illustrated a deflecting device generally designated 120,entirely positioned within the common carotid artery 38. The device 120is fitted with three deflecting surfaces 122 (the number of deflectingsurfaces and their design may vary depending on the desired hemodynamicparameters).

[0044] The arrangement is such that embolic material (represented byflow lines 126) flows via CCA 38, encounters deflecting surfaces 122 andrather than entering the ICA 40 is deflected into the ECA 42. As will beapparent to the skilled person, the flow lines of the embolic materialare dictated by the arrangement of the deflecting surfaces 122, and canbe calculated on the basis of the blood flow parameters. The deflectingelements are non-occluding, inasmuch as they allow the flow of some ofthe blood to proceed through openings provided therein, wherein theopenings are delimited by wire-like or rod-like members of definedthickness.

[0045] A preferred embodiment of the device of FIG. 1 is shown in FIG.2. The deflecting device 120 is provided with deflecting surfaces 122,the direction of blood flow being that of arrow f. The deflectingsurfaces are seen in FIG. 2B to be, according to this particularembodiment of the invention, made of a wire mesh, which is enlarged inFIG. 2C and is seen to have a square side dimension “a”, and a wirethickness “t”. The holes in the wire mesh of deflecting surfaces 122 aresignificantly smaller than the holes 123 found elsewhere in thedeflecting device 120.

[0046] Delivery of the device is facilitated, as shown in FIG. 2D, ifwhen the stent-like device is in collapsed form, the deflecting surfacesare essentially parallel to its surface. Expansion of the stent-likedevice leads to the raising of the deflecting surfaces and to theirpositioning illustrated in FIG. 2A This arrangement can be easily deviseby the skilled person, and is therefore not disclosed herein in detail,for the sake of brevity.

[0047] In FIG. 3A, there is illustrated still another embodiment of adeflect device 204 received and anchored within the CCA 38. The device204 comprises a helical structure of fine wires 206 which have atheoretical point of insertion shifted from the longitudinal axis of theartery 38. This can be understood from FIG. 3B which is a view throughthe CCA 38.

[0048] The arrangement is such that a helical movement is imparted tothe embolic material flowing through the CCA 38, which is thus deflectedinto the ECA 42. This is further illustrated in FIG. 4. FIG. 4A shows incross-sectional view of the helical deflecting element is positionedwithin the vessel. As seen in FIG. 4B, it is desirable to have the wholelength of the helix last essentially the whole diameter of the ICA, toensure that embolic material is deflected away from the opening.

[0049] The construction of the helical device of the preferredembodiment of FIG. 4A can be as in FIG. 4C, in which a frame 300 isequipped with struts (stages) 301, to form a ladder-like structure. Thenumber of struts 301 may vary, according to the desired dimensions ofthe device. Intermediate strengthening elements 302 can be inserted, forstrength reasons, between any pair of struts 301. Furthermore, more thanone strengthening element can be provided between a pair of struts, andsome or all pairs may be without any strengthening element, the numberand nature of said strengthening elements being dictated solely bymechanical considerations. The frame 300 can be constructed so as to be“normally helical”, viz., such that its normal configuration is that ofFIG. 4A, and that a force must be exerted on it to bring it to theconfiguration of FIG. 4C. In order to deliver it, the ladder-likeelement of FIG. 4C is allowed to coil itself from a distended position,onto a portion of the circumference of a cylindrical delivery device(not shown). Withdrawal of the delivery device causes the device toassume its normal, helical position. The device, when in place, lookfrom an axial direction of the CCA as schematically shown in FIG. 4D.The arc-like structure 310 shown on the left side of FIG. 4D representsthe beginning of said ladder-like elements, and is in contact with theendothelial surface of the vessel wall.

[0050] Typical illustrative and non-limitative dimensions for the deviceof FIG. 4C are:

[0051] a—distance between stages—400μ;

[0052] t₁—thickness of the struts—10-50μ;

[0053] t₂—frame thickness—200μ;

[0054] The device of the invention can be constructed in a way verysimilar to cardiac stents, although the dimensions are different and,therefore, allow for greater constructive flexibility. However, the manof the art will easily recognize the materials and expandable shapessuitable to make the stent of the invention. For instance, the stent andthe deflecting device can be made of a material selected from nitinol,polymeric material, stainless steel, etc., and having a configurationselected from zigzag shape and sinusoidal shape. The filtering means ofthe deflecting device, if used, should have the following dimensions, inorder to effectively prevent the entrance of at least a major part ofdangerous embolic material: >200-400 μm. The diameter of the stent maysomewhat vary for different individuals. However, the diameter in theclosed state is Up to about 3 mm, while when expanded, the diameter mayvary in the range of 5 mm to 10 mm. The diameter of the wire which makesup the body (or anchoring portion) of the device is preferably in therange 100 μm to 200 μm, while that of the wire used for the filteringdevice is preferably in the range of 10 μm to 200 μm. Of course, theentire device can also be constructed using the same dimensions, so thatthere is no difference in mesh size between the body of the device andits deflecting portion.

[0055] Any suitable method can be used to manufacture the device of theinvention, such as laser cutting or chemical etching. These methods areconventional and well known to the skilled person, and are therefore notdiscussed herein in detail, for the sake of brevity. Additionally,markers can of course be provided, which are visible by any suitabletechnique, e.g., X-ray, to enable to impart to the stent the desiredspatial position, such as marker 303 in FIG. 4A.

[0056] The device of the invention must fulfill certain predeterminedconditions that will be detailed hereinafter. The skilled person will ofcourse be able to devise various devices, of different shapes andproperties, which fufill said conditions. When testing a device of theinvention under physiological conditions, namely:

[0057] Re_(av)=200-500

[0058] BPM (beats per minute)=40-180

[0059] Womersley=2-7

[0060] wherein Re_(av) is the average Reynolds number, and Womersley isthe dimensionless beat parameter;

[0061] the following conditions should preferably be met by the deviceof the invention:

[0062] 1) Re_(prox) between 0 and 4, preferably 1 or less (creeping orStokes' flow)

[0063] 2) 100 dyne/cm²>Shear Stress>2 dyne/cm²

[0064] 3) The generation of thrombin should not exceed 40 nmole/minute,as measured according to the thrombin acetylation test.

[0065] wherein Re_(prox) is the Reynolds number for the wire of whichthe deflect element is made, and the shear stress is measured at thedevice. As will be appreciated by the skilled person, the smaller theRe_(prox) number the better. However, devices attaining larger Re_(prox)numbers than indicated above may also be provided, and the invention isby no means limited to any specific Re_(prox) number.

[0066] While some preferred embodiments of the invention have beenillustrated and described in the specification, it will be understood bya skilled artisan that it is not intended thereby to limit thedisclosure of the invention in any way, but rather it is intended tocover all modifications and arrangements falling within the scope andthe spirit of the present invention. For example, the deflecting devicemay be a permanent device or may be removed from the vicinity of thecarotid arteries at need Furthermore, the deflecting member may beintegrally formed with, or detachably connected to, the anchoringmember, wherein in some instances it might be necessary first toposition the anchoring member and then to attach the deflecting member.Additionally, the deflecting member may be of different size, shape andpattern, depending on flow parameters and patient specific requirements.

1. An implantable device for positioning in the vicinity of thebifurcation of the common carotid artery (CCA) into the internal carotidartery (ICA) and the external carotid artery (ECA), comprising adeflecting element suitable to deflect the flow of embolic materialflowing in the CCA toward the ICA, into the ECA, without filtering. 2.An implantable device according to claim 1, comprising an anchoringmember engageable with the inner walls of a carotid artery, and one ormore deflecting members.
 3. An implantable deflecting device accordingto claim 2, wherein at least the anchoring member is a stent adapted forinsertion via the vasculature of an individual.
 4. An implantabledeflecting device according to claim 2, wherein one or more deflectingmember is integrally formed with the anchoring member.
 5. An implantabledeflecting device according to claim 4, wherein the one or moredeflecting member has a wing-like shape.
 6. An implantable deflectingdevice according to claim 1, comprising a deflecting member consistingof two or more sets of parallel wires extending obliquely with respectto the axis of flow and also inclined with respect to a plane normal tosaid axis.
 7. An arterial stent suitable to be positioned in thevicinity of the bifurcation of the common carotid artery (CCA) into theinternal carotid artery (ICA) and the external carotid artery (ECA),comprising a deflecting device.
 8. A stent suitable to be positioned inthe vicinity of the bifurcation of the common carotid artery (CCA) intothe internal carotid artery (ICA) and the external carotid artery (ECA),coupled to a deflecting device.
 9. A method for preventing the flow ofembolic material flowing in the CCA from accessing the ICA, comprisingdeflecting the flow of said embolic material into the ECA.
 10. A methodaccording to claim 9, comprising implanting in the vicinity of thebifurcation of the common carotid artery (CCA) into the internal carotidartery (ICA) and the external carotid artery (ECA), a deflecting devicecomprising a deflecting element suitable to deflect the flow of embolicmaterial flowing in the CCA toward the ICA, into the ECA.
 11. A methodfor treating a patient suffering from, or suspected of suffering from,the generation of embolic material, comprising deflecting the flow ofsaid embolic material into the ECA.
 12. A method for preventingcerebralvascular diseases or their recurrence, comprising implanting inthe vicinity of the bifurcation of the common carotid artery (CCA) intothe internal carotid artery (ICA) and the external carotid artery (ECA),a deflecting device comprising a deflecting element suitable to deflectthe flow of embolic material flowing in the CCA towards the ICA, intothe ECA.
 13. A method according to claim 12, wherein thecerebralvascular disease is a stroke.
 14. A method according to claim12, wherein the deflecting device is provided in, or coupled to, astent.
 15. An implantable device according to claim 1, wherein thedeflecting element is provided with wire-like or rod-like members havinga thickness comprised between 10-50μ.
 16. An implantable deviceaccording to claim 15, wherein the deflecting element is such thatReynolds number for the wire-like or rod-like member under physiologicalconditions is between 0 and 4, preferably 1 or less.